wavel.	cross section	error limit

240	6.2e-19		1.2e-19
245	4.6e-19		9.0e-20
250	4.0e-19		8.0e-20
260	3.1e-19		6.0e-20
265	2.3e-19		5.0e-20
270	2.2e-19		4.0e-20
280	1.7e-19		3.0e-20